The present invention relates to novel aryl- or aralkylbenzenes having two benzene rings at least one of which is substituted by at least one 3,3,3-trifluoropropyl group and also to a novel process for producing them. An aryl- or aralkylbenzene having two benzene rings at least one of which is substituted by at least one 3,3,3-trifluoropropyl group is expected to be, for example, a dielectric material.
As a means for synthesizing such aromatic compounds having a benzene ring substituted by 3,3,3-trifluoropropyl group, only one process has been proposed (U.S. Pat. No. 3,080,428), in which 3,3,3-trifluoropropyl ether, (CF.sub.3 CH.sub.2 CH.sub.2).sub.2 O, is brought into reaction with benzene in the presence of hydrogen fluoride to obtain (3,3,3-trifluoropropyl)benzene. However, since in the above-mentioned process, water is formed by the reaction, the activity of the catalyst is reduced during the reaction, and the recovery of once-used catalyst is difficult. Moreover, 3,3,3-trifluoropropyl ether as the starting material is synthesized by the reaction of hydrogen fluoride, formaldehyde (or its polymer) and vinylidene fluoride. Accordingly, 3,3,3-trifluoropropyl ether is expensive because of the high price of vinylidene fluoride and of the yield of synthesizing the ether as being low as 50 to 60%.
It is an object of the present invention to provide a trifluoropropyl derivative of aryl- or aralkylbenzene of the general formula: ##STR2## wherein R is a not-substituted or substituted phenyl group, benzyl group, phenethyl group or alpha-methylbenzyl group by 3,3,3-trifluoropropyl group and n is 1, 2 or 3, provided that the total number of 3,3,3-trifluoropropyl group in said trifluoropropyl derivative of aryl- or aralkylbenzene is at most 3. A further object is to provide a process for producing an aryl- or aralkylbenzene having at least one benzene ring substituted by at least one 3,3,3-trifluoropropyl group, which comprises bringing an aryl- or aralkylbenzene of the formula ##STR3## wherein R.sup.1 represents phenyl group, benzyl group, phenethyl group or alpha-methylbenzyl group, into reaction with 3,3,3-trifluoropropylene in the presence of an acid catalyst, such as hydrogen fluoride or boron trifluoride. In addition, the reaction between biphenyl and 3,3,3-trifluoropropylene may also be carried out in the presence of a mixture of hydrogen fluoride and boron trifluoride as the catalyst.
Other object is to provide a dielectric material comprising at least one 3,3,3-trifluoropropyl derivative of aryl- or aralkylbenzene. Another object is to provide a substituted aryl- or aralkylbenzene by 3,3,3-trifluoropropyl group obtained by bringing aryl- or aralkylbenzene into reaction with 3,3,3-trifluoropropylene in the presence of an acid catalyst, and separating said substituted aryl- or aralkylbenzene from the resultant reaction mixture. Still other objects and advantages of the present invention will become apparent hereinafter.